# CHemistry chapter 2 2

## Terms

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scientific method
a logical approac to solving problemsby observing and collectiong data, formulating and testing hypothesis, and formulating theories that are supported by data.
observing
the use of senses to obtain information it involves measurements and collecting data.
Qualative vs. quantitative information
Qualative is descriptive and quantitative is numerical
a system is a
a apecific protion of matter ina given region of space that has been selected for study during an experiment.
hypothesis
a testable statement
model
used to represent ideas which cannot be easily viewed
theory
broad generalizations used to explain observations.
quantity
something that has magnitude, size or amount
SI system
the system internationale which includes 7 base units, also known as the metric system
measurement standard
an object or natureal ohenomena that is of constant balue, easy to preserve and reproduce, and pratical in size
-a means of comparison
length
mass
time
temperature
amount of substance
electric current
luminous intensity
energy
meter
kilogram
second
kelvin
mole
ampere
candela
jule
Celsius to Kelvin
degree C + 273 =K
king henry died (monday)(laughing) (greedy) drinking chocolate milk
km-hm-dam-m-dm-cm-mm
kl-hl-dal-l-dl-cl-ml
kg-hg-dag-g-dg-cg-mg
dimensional analysis or factor label method
method of solving problems based on cancellation of units
formula for density
D=m/v
density equals mass divided by volume
how do you find the volume of irregularly shaped objects
water displacement
volume of cylinders
V= pi(r)2(h)
what is accuracy
what is precision
repeatability of a measurement, how many times you come close.
percent error is calculated by
value (accepted)- value(experimental)/ value(accepted) x 100.
significant figures are
valid figures actually obtained form a measurement.
what are the rules for determining the number of significant figures.
- all nonzero digits are significant
-captive zeros are significant
-trailing zeros may or may not be significant
exact and perfect numbers
measurements or counting and are infinite number of solutions.
what is a graph
a picture of data
rules for making a good graph are
-you label each axis with a unit and a description
-divide each axis evenly
-plot and circle data points
-draw a best fit line between data points
how do you find the slope
rise over run
direct and indirect proportions
direct- when one goes up the other quantity goes up too
indirect- when one goes up the other goes down.(hyperbola)
conversion factor
a ratio derived from the equality between two different units that can be used to convert from one unit to the other.

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